Power semiconductor devices such as power MOSFETs are prevalent in power supply applications. For example, power MOSFETs are used as synchronous rectifiers in power supply circuits.
Many power MOSFETs are known to include a body diode, which conducts current under reverse voltage conditions. The body diode of a power MOSFET exhibits relatively high resistance to current and thus dissipates much power. To avoid this undesirable consumption of power it is known to connect a Schottky diode across the body diode of a power MOSFET when, for example, the MOSFET is used as a synchronous rectifier, in order to reduce power loss during reverse voltage conditions. According to one conventional concept, for example, a discrete power MOSFET and a discrete Schottky diode are copackaged. According to another known concept a power MOSFET and a Schottky diode are formed in a single die to obtain a monolithic integrated device. One such device is illustrated by U.S. Pat. No. 6,351,018 ('018 patent). In that device, the source contact and the drift region of the MOSFET form a schottky diode. Thus, in a device according to the '102 patent the drift region has to be configured in order to make a Schottky device. To be specific, factors such as the resistivity of the drift region have to be designed for a Schottky device, which may not be desirable as it may increase the overall resistance of the device.